Due to the ever-increasing use of communication between not only people, but also things and the use of wireless local area networks, such as IEEE802.11 radios in low power devices, power management has become a critical feature. For example, the current IEEE802.11 standard allows devices to be either in an Active mode (radio always on) or a Power Save (PS) mode. A device may indicate that it switches between these states by changing a Power Management field in a Frame Control field of the Media access control Protocol Data Units (MPDUs) it sends. A device in PS mode is said to be in an Awake state when its radio is on, and in a Doze state when its radio is off. An access point device (AP) buffers traffic intended for devices in the PS mode, and informs devices of this buffered information using the Traffic Information Map (TIM) which is broadcast by the AP in every beacon frame. A device in the PS mode wakes up periodically to receive the beacons and learn from the TIM if there is any data buffered for it. The standard does not require reception of every beacon; leaving it at the discretion of the PS device, as long as it does not loose association with the AP. The TIM element indicates downlink buffered data for all stations (STAs) in the Basic Service Set (BSS). In 802.11ah, where the number of PS devices may be large, it is also possible to split the TIM into several segments and transmit each segment in a different beacon under a scheme called ‘page slicing’. In this case, a PS device wakes up periodically to listen to a special beacon (transmitted by the AP at approximately predictable intervals) that carries the page slicing information.
U.S. Pat. No. 7,231,221 discloses an access scheme in a communication system which can deal with a mix of devices having different power constraints and different latency requirements and allow highly asymmetric latency behaviour. Such a communication system may include a central control station that broadcasts beacon messages on a communication channel, such as a radio channel, and at least one remote terminal that accesses a communication channel based on the beacon messages. The beacon messages are configured such that individual access to the communication channel by each terminal is controlled according to a grouping of the terminals into respective beacon groups. Each beacon group may have a corresponding beacon message, and beacon messages corresponding to different beacon groups may be broadcast at staggered time intervals. Although this is an efficient way of enabling the terminals to operate on a lean energy budget, at least the demand for remote electronic entities with very lean energy budgets to interact with a communication network calls for further advances in power saving.